In the field of fuel cells, there is an attempt to increase fuel cell performance, focusing on a catalyst-supporting support.
For example, in Patent Literature 1, it is disclosed to modify the surface of a carbonaceous material that is used as a support, by hydrophilization of the material (paragraph 0089 in Patent Literature 1).
Patent Literature 2 discloses an electrode catalyst for a fuel cell, which is uniformly supported on the surface of a mesoporous carbon support since the average pore diameter of the support corresponds to the average particle diameter of a catalyst complex.
Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2015-071784
Patent Literature 2: JP-A No. 2015-076277
However, if the surface of the support is hydrophilized too much, flooding may occur when a fuel cell is in a wet state, and the power generation performance of the fuel cell may decrease.
If the support is hydrophilized before the catalyst is supported thereon, the surface state of the support may be changed when the catalyst is supported thereon, and the surface of the catalyst may not be appropriately covered with an ionomer.